DLP projectors (and indeed TV, Single Chip) flash parts of a colour one after the other to make the illusion of the whole colour (using your eye/brain visual processing) whereas LCD models project all 3 primary colours (RGB) at the same time so the colour projected is the colour you see, they're also vibrant & natural colours.

It's our opinion (not a fact) that people who suffer motion sickness, migraines or are epileptic should consider avoiding single chip DLP. Just an opinion based on our experience. Do some research on flashing lights or strobes as a starting point. Another problem with some DLP projectors is the bearing on the colour wheel becomes noisy and/or fails as it's spinning at a very fast speed.

Most people can see "Rainbows" (RBE) once they know what to look for, put another way they thought the artifacts were normal. Some people knock us (normally forums) for showing this information but they are not in the firing line, they have not had to issue refunds and often they are simply defending their purchase, which is understandable. They can also be people selling just DLP.

Many people love their DLP displays. It depends on how sensitive you are to the sequential (flashing) nature of the system. We got into hot water for even suggesting that people who get motion sickness may be in the group to avoid SC DLP that was an observation based on our experience only.

At the and of the day you make your own decision but ask why so many manufacturers (even ones that were DLP ) now use 3-LCD in their home cinema models. -- AIM

|Full size here|

This review contains statements of pure opinion and fair comments made in good faith in the interest of the public by AIM Digital Imaging. To ascertain the facts please do your own research. There are also quotes from and links to external sources please see their disclaimers.

Once you've seen rainbows (or RBE) you can't miss them.

• In our opinion if you're easily motion sick, have congenital nystagmus or you're sensitive to flashing lights and your budget is under 15K buy a LCD for most applications.
|Australia only pre-sales support contact us when you're ready to buy.. |
• Our personal experience is people who suffer motion sickness may also be prone to being "DLP sensitive" but this is just our observation only it has no scientific basis.
• Remember it may be a person watching it, not you that has the problem, that's why we (and others) would not recommend installing 1 chip DLP one in a public place.

"..3-chip DLP systems do not have any RBE because they do not require a color wheel. DLP, however, seems to think that DLP chips are worth more than gold and so, for now, 3-chip DLP projectors cost about 10x the price of entry level 3LCD projectors. Perhaps someday soon they will loosen their grip on the market and the color wheel can finally die the quick but painful death it deserves.."
summary

www.avsforum.com/avs-vb/archive/index.php/t-902701.html

Flashing Lights used as a weapon!

According to Lieberman, the device flashes LED lights at several specific frequencies.

Before your brain has time to adjust to one frequency, the Incapacitator flashes another. Add multiple colors and random pulses and the brain just can't keep up.

"Let's not pretend these are anything less
than a weapon," said Michael Soller of the ACLU

"The longer you look at this, the more you don't want to look at it," said Lieberman. "The closer you are to it, the more intense the effect."

The only ways to escape the effects? "Close your eyes, put your hand up, turn your head away, all of which will give the user the advantage they need," said Lieberman.

"..The flashes temporarily blind a person, as any bright
light would, and the light pulses, which quickly change both in color and duration, also cause what Lieberman calls psychophysical effects. These effects, whose effectiveness depends on the person, range from disorientation to vertigo to nausea, and they wear off in a few minutes.

It’s not clear why the changing light pulses cause this effect, even though the effect has been well documented, Lieberman says Helicopter pilots, for example, have been known to crash because they get disoriented by the choppy flashes of sunlight coming through the chopper’s spinning blades.."

The point of this device is to disorient you, so we modified the video when we showed it on air.

http://www.time.com/time/specials/2007/article/0,28804,1677329_1678438_1...

Many people can't see Rainbow Effect on a DLP because they don't know what to look for...

the link that was posted on this forum which had an animated example of rainbow effect has been quite usefull...I have shown it to many people who claim to not be able to see RBE and they all said "oh THAT, yes I have always seen that!"

A segment of animated footage promoting the 2012 Olympics has been removed from the organisers' website after fears it could trigger epileptic seizures.
London 2012 Olympics branding film causes epileptic seizures
One thing to keep in mind when introducing any kind of flashing on the Web is the possibility of it causing seizures in people who have photosensitive epilepsy. It’s one of the basics of Web accessibility, and the fact that flashing or strobing can trigger epileptic seizures is widely known even among people who do not work in the field of accessibility.

I was first made aware of it back in the early nineties, when I used to do a bit of DJing. I loved using the strobes, but after a girl came up to the DJ booth one night to tell me she’d had an epileptic seizure caused by strobing lights I stopped using them. Strobes are cool, but not when you know they may trigger a seizure in someone on the dance floor.

But it seems that knowledge of the connection between strobing or flashing lights and epilepsy attacks is not as widespread as I thought. Recently a movie clip that was published on the official London 2012 Olympic Games website (Warning! Contains colour combinations that are painful to look at. Yes, really.) contained an animation that caused seizures in at least thirty people. And those are just the people who contacted the charity Epilepsy Action about it.

[NOTE it looks like they have removed the offending flashing logo.. It would be a brave epileptic that knowingly purchased a single chip DLP projector after seeing all the available information in our opinion.. -- AIM]

The same film, created to promote the London 2012 brand, was shown on television, where it also triggered seizures. This is a bit more surprising than the film being published on the website, since there are machine-testable regulations for television footage that make sure it does not trigger seizures in people with photosensitive epilepsy. The London 2012 ad was apparently not tested, and consequently did not comply with the Ofcom safety guidelines, as mentioned by BBC News in Epilepsy fears over 2012 footage.

The film has since been re-edited to remove the seizure-triggering segment. Accessibility issues aside, the logo for the London 2012 Olympic Games has been talked about in plenty of forums. I’ll settle for saying that I’ve seen many logos that are better, but Jack Pickard has a bit more to say about it in London Logo No Go. Hint – he is not overly enthusiastic about it ;-)

The DLP "Rainbow Effect"
This visual artifact is best described as brief flashes of perceived red, blue, and green "shadows" observed most often when the projected content features bright/white objects on a mostly dark/black background (the scrolling end credits of many movies are a common example). Some people perceive these rainbow artifacts all of the time, while others say they only see them when they let their eyes pan across the image. Yet others do not notice the artifact at all. The effect is likely rooted in the concept of the flicker fusion threshold .

The "Rainbow Effect" is unique to single-chip DLP projectors. As described above, only one color is actually displayed at any given moment. As the eye moves across the projected image, these separate colors become visible, resulting in a perceived "rainbow". The manufacturers of single-chip DLP projection systems have used color wheels rotating at higher speeds, or with more color segments, in order to minimize the appearance of the artifacts. These are referred to as 2x, 3x or 4x wheels. For example, a six segment wheel(RGBRGB) rotating at two revolutions per frame would be a 4x wheel.

Another way to reduce the rainbow effect is to replace a segmented wheel with a wheel whose colors are in an Archimedean spiral . This forms bands of color that move down (or up) the screen. With segmented wheels, the DMD must "go black" while the wheel transitions from one color to another. Not only can this interfere with persistence of vision and thus accentuate the rainbow effect, it means that the more segments there are, the darker the display will be, all else being equal. With a spiral wheel, the mirrors can display more than one color at a time, each moving down (or up) as the wheel turns.

The LED light packs now being introduced in DLP projectors may eliminate rainbow effect for all but a few very sensitive viewers thanks to their high switching frequency and a complete lack of "black" segments as described above. Additionally, the LED pack can display any color of light at any intensity, a capability which, if exploited, provides the potential for increased color gamut and improved contrast compared to displays employing color wheels with fixed-color segments.

Source http://en.wikipedia.org/wiki/DLP who no doubt will have legal action coming too :)

A Potential Problem with DLP: The Rainbow Effect

If there is one single issue that people point to as a weakness in DLP, it is that the use of a spinning color wheel to modulate the image has the potential to produce a unique visible artifact on the screen that folks refer to as the "rainbow effect," which is simply colors separating out in distinct red, green, and blue. Basically, at any given instant in time, the image on the screen is either red, or green, or blue, and the technology relies upon your eyes not being able to detect the rapid changes from one to the other. Unfortunately some people can. Not only can some folks see the colors break out, but the rapid sequencing of color is thought to be the culprit in reported cases of eye strain and headaches. Since LCD projectors always deliver a constant red, green, and blue image simultaneously, viewers of LCD projectors do not report these problems.

How big of a deal is this? Well, it is different for different people. For some who can see the rainbow effect, it is so distracting that it renders the picture literally unmatchable. Others report being able to see the rainbow artifacts on occasion, but find that they are not particularly annoying and do not inhibit the enjoyment of the viewing experience. Fortunately, the majority of the population either cannot detect the rainbow artifacts, or if they can they are not overly bothered by them. The fact is if everyone could see rainbows on DLP projectors the technology never would have survived to begin with, much less been embraced by so many as a great technology for home theater video systems. Nevertheless, it can be a serious problem for some viewers.

Source http://www.projectorcentral.com/lcd_dlp.htm

DLP vs. LCD - Which is Better?

The potential drawback of this single-chip DLP technology is that in any given instant, the picture on the screen is not the total image, but is instead rapidly alternating between images consisting of the individual red, green, and blue colors. Thus the eye and the brain play the last critical role in making single chip DLP projectors work, by combining or averaging or integrating the picture, so that the viewer perceives the desired image and not the rapidly flashing momentary components of the image.

With a static picture from a single-chip DLP-based projector, it is easy to understand how this averaging works just fine. Where things potentially start to fail is when there is motion in the image, or when one blinks or rapidly moves one's eyes quickly between various parts of the image. In these cases, the perceptual integration of the image may break down and one might see "rainbows" or false flashes of color, in the image. Some individuals have also reported getting headaches after watching single-chip DLP projectors for any length of time. It appears that not all individuals handle this color averaging process equally well. Newer single-chip DLP-based projectors use a higher speed (5x) six segment color wheel, thus greatly reducing the likelihood that an individual will perceive these artifacts. Also, Double Data Rate (DDR) DMD chips reduce artifacts even further by updating the information going to each mirror at a faster rate.

Source http://www.hometheaterhifi.com/volume_10_3/feature-article-dlp-vs-lcd-wh...

Forums

My personal experience is that I was also highly susceptible to them when I first viewed the X1 DLP projector. Indeed, after my first hour of viewing I felt a nauseous headache coming on (I also get car sick by the way - so perhaps this is an indication?).

Source http://www.audioenz.co.nz/forums/archive/index.php/t-561.html

Visual Fatigue

Visual Fatigue in Congenital Nystagmus Caused by Viewing Images of Color Sequential Projectors (DLP 1x Chip) - Journal of Display Technology- Vol.1- No.2 - pp.314 - 320

Masaki Ogata, Kazuhiko Ukai and Takashi Kawai

Color breakup is the perceived splitting of the white portions of an image into its red, green, and blue components when the image is projected with the color sequential method and the viewer is moving his or her eyes. This study aims to evaluate how color breakup affects symptoms of visual fatigue in people with congenital nystagmus. The eyes of people with congenital nystagmus continuously oscillate leading to color breakup without pause. One in every 1 500 persons is afflicted with congenital nystagmus.

Many sufferers have almost no symptoms in daily life except for a mild deterioration of visual acuity. Five subjects with congenital nystagmus were shown a 15-min portion of a movie projected with three video projectors (one liquid cyrstal display (LCD) projector and two single-chip digital light processing (DLP) projectors). They were subjectively evaluated both pre- and post-viewing with a questionnaire listing visual fatigue symptoms. One subject was tested in an additional experiment using six more projectors.

Results indicated that subjects with congenital nystagmus felt severe visual fatigue after they viewed images produced by color sequential projectors. Mechanism of the cause of visual fatigue is not clear in general and in color breakup in congenital nystagmus, however, it was clear that people with nystagmus felt continuing color breakup as a flickering image. Flickering light is a major cause of visual fatigue.

Color sequential projectors are best avoided in public settings, such as classrooms, lecture theaters and conference sites."

Source http://www.audioenz.co.nz/forums/archive/index.php/t-561.html

The 3LCD

Group is also producing collateral materials and advertisements for consumers and industry professionals that further rein- force many of the core benefits of 3LCD prod- ucts as shown at CES. These include: a.. "No Color Breakup" - since this technology simultaneously projects three full-time red, green and blu e images, there is no color breakup or " rainbow effect" to potentially cause viewers eyestrain or visual fatigue.
Visual fatigue in congenital nystagmus caused by viewing images of color sequential projectors
Ogata, M. Ukai, K. Kawai, T.
Sch. of Sci. & Eng., Waseda Univ., Tokyo, Japan;
This paper appears in: Display Technology, Journal of
Publication Date: Dec. 2005
Volume: 1, Issue: 2
On page(s): 314- 320
ISSN: 1551-319X
INSPEC Accession Number: 8677107
Digital Object Identifier: 10.1109/JDT.2005.858918
Posted online: 2005-12-05 08:50:16.0

Abstract Color breakup is the perceived splitting of the white portions of an image into its red, green, and blue components when the image is projected with the color sequential method and the viewer is moving his or her eyes.

This study aims to evaluate how color breakup affects symptoms of visual fatigue in people with congenital nystagmus. The eyes of people with congenital nystagmus continuously oscillate leading to color breakup without pause. One in every 1500 persons is afflicted with congenital nystagmus. Many sufferers have almost no symptoms in daily life except for a mild deterioration of visual acuity. Five subjects with congenital nystagmus were shown a 15-min portion of a movie projected with three video projectors (one liquid crystal display (LCD) projector and two single-chip digital light processing (DLP) projectors). They were subjectively evaluated both pre- and post-viewing with a questionnaire listing visual fatigue symptoms. One subject was tested in an additional experiment using six more projectors. Results indicated that subjects with congenital nystagmus felt severe visual fatigue after they viewed images produced by color sequential projectors. Mechanism of the cause of visual fatigue is not clear in general and in color breakup in congenital nystagmus, however, it was clear that people with nystagmus felt continuing color breakup as a flickering image. Flickering light is a major cause of visual fatigue. Color sequential projectors are best avoided in public settings, such as classrooms, lecture theaters and conference sites.

Source http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1545796

Looking for a projector that won't have this problem?

Have a look at some of the 1080P LCD models by Epson, Panasonic and Sanyo.

This review contains statements of pure opinion and fair comments made in good faith in the interest of the public by AIM Digital Imaging. To ascertain the facts please do your own research. There are also quotes from and links to external sources please see their disclaimers.